The present invention relates generally to a polymercaptan material and the preparation thereof which is useful in the curing process of epoxy resin materials for use in applications where there is frequent contact with water. More particularly, the present disclosure relates to a propoxylated ether polythiol of the structure: ##STR3## WHEREIN Y IS AN INTEGER OF AT LEAST 1, X IS AN INTEGER OF AT LEAST 2 AND R is a polyol consisting of atoms of carbon, hydrogen and oxygen and free of reactive functional groups and the total number of carbon atoms in R and ##STR4## IS GREATER THAN 15.
The term epoxy resins is a trivial name given to a class of polymers prepared by a step-growth polymerization of a bifunctional alkylene epoxide with a bifunctional or polyfunctional nucleophile. The polymers prepared are essentially linear, low molecular weight fusible prepolymer polyethers with reactive epoxide end groups commonly referred to as epoxy resins. These resins, when combined with the proper curing agents such as polymercaptans, provide thermoset polymers exhibiting a high degree of chemical resistance, outstanding adhesion to most substrates, low shrinkage, and good impact strength and flexibility. The principal applications for the thermoset polymers are binders for industrial baking finishes, high performance maintenance and marine coatings, adhesives, reinforced plastics, electrical potting and encapsulation and matrices for industrial flooring and wall panels utilized in building construction. Many of these applications involve contact with water and climatic elements. Therefore it is a matter of concern when these thermoset polymers absorb water to the extent that the adhesive bonds break or the corrosion resistance of the material is impaired as to cause failure or other undesirable defects within the material. Although maximizing the properties of the resultant thermoset polymers both chemically and physically is a desirable aim, consideration must be given to the cure rate and cure properties of a given material along with undesirable characteristics of the components to make these thermoset polymers such as the distinctly undesirable olfactory characteristics of polymercaptans as well as the expense involved in use of such polymercaptans in these thermoset polymers.
It would therefore be highly desirable to be able to produce a thermoset polymer derived from epoxy resins that would meet many of the above-described criteria utilizing a polymercaptan for curing the epoxy resin to obtain materials for uses especially subject to the climatic elements such as water.